refactor(js): avoid use of window.XXX and move to import/export

- change worker: do not cache html pages (not necessary)
- remove use of window.XXX and maximize import/export,
  this will provide more clarety,
  show circular dependencies + you will benefit IDE help

static/js/app/bootstrap.js

@@ -2,13 +2,10 @@
  * OxiCloud - App bootstrap
  * Isolated startup trigger for the main application initializer.
  */
+import { initApp } from './main.js';
 
 if (document.readyState === 'loading') {
-    document.addEventListener('DOMContentLoaded', () => {
-        if (typeof window.initApp === 'function') {
-            window.initApp();
-        }
-    });
-} else if (typeof window.initApp === 'function') {
-    window.initApp();
+    document.addEventListener('DOMContentLoaded', initApp);
+} else {
+    initApp();
 }